JP4996661B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire having improved block rigidity while maintaining drainage performance by improving the wall shape of the block.

  A pneumatic tire having a block pattern in which a plurality of blocks are formed in a tread portion is known. In this type of pneumatic tire, the stability of the steering and the wear resistance are improved by increasing the rigidity of the block. In order to increase the rigidity of the block, for example, increasing the land ratio, making the wall surface of the block a gentle slope, and further decreasing the depth of the groove in the tread portion are known.

  However, each of the above methods involves a reduction in the groove volume, and thus has a problem that drainage performance, particularly hydroplaning performance, is deteriorated. Thus, the increase in rigidity of the block and the drainage performance have a trade-off relationship, and it has been difficult to achieve both. Related technologies include the following.

JP 2002-59711 A JP 2004-182074 A JP 2007-45233 A

  The present invention has been devised in view of the above problems, and is directed to the tire circumferential direction of the block outer edge, which is the intersection line between the block wall surface and the tread surface, and the block inner edge, which is the intersection line between the block wall surface and the groove bottom. The main purpose is to provide a pneumatic tire capable of improving the steering stability performance by increasing the rigidity of the block while maintaining the drainage performance on the basis of defining each angle within a certain range.

The invention according to claim 1 of the present invention is a pneumatic tire in which a rotation direction is specified, and a tread portion includes a longitudinal groove on a tire equator side, a longitudinal groove on a ground contact end side, and a tire rotation direction. It comprises a block divided by a lateral groove on the first arrival side and a lateral groove on the rear arrival side in the tire rotation direction, the block comprising a tread surface that contacts the road surface, a vertical wall surface on the tire equator side, and a ground end side A longitudinal wall surface, a lateral wall surface on the tire rotation direction first arrival side, a lateral wall surface on the tire rotation direction rear arrival side, and a first block outer edge that is an intersection line of the longitudinal wall surface on the tire equator side and the tread surface The angle with respect to the tire circumferential direction is α1U, the angle with respect to the tire circumferential direction of the inner edge of the first block that is the intersection of the vertical wall surface on the tire equator side and the groove bottom of the longitudinal groove on the tire equator side is α1L, and The line of intersection between the vertical wall surface on the grounding end side and the tread surface The angle of the second block outer edge with respect to the tire circumferential direction is α2U, and the tire circumferential direction of the inner edge of the second block that is the intersection of the vertical wall surface on the ground contact end side and the groove bottom of the vertical groove on the ground contact end side When the angle with respect to is α2L, the following expressions (1) to (4) are satisfied.
5 degrees ≦ α1L <α1U ≦ 30 degrees (1)
10 degrees ≦ α2L <α2U ≦ 35 degrees (2)
α1L <α2L (3)
α1U <α2U (4)

  According to a second aspect of the present invention, the block is formed by a vertical wall surface on the tire equator side and a normal line of a tread standing on the outer edge of the first block in a block cross section orthogonal to the outer edge of the first block. The first wall angle θ1 gradually increases from the tire rotation direction first arrival side toward the rear arrival side, and the block has a vertical wall surface on the ground contact end side in a block cross section orthogonal to the second block outer edge; 2. The pneumatic tire according to claim 1, wherein a second wall surface angle θ <b> 2 formed by a normal line of the tread standing on the outer edge of the second block gradually increases from the rear arrival side to the first arrival side in the tire rotation direction.

  According to a third aspect of the present invention, the block includes the first wall surface angle θ1c at the end portion on the tire rotation direction first arrival side and the first wall surface angle θ1k at the end portion on the rear arrival side in the tire rotation direction. The pneumatic tire according to claim 2, wherein a difference in angle θ1k−θ1c with respect to is 2 to 45 degrees.

  According to a fourth aspect of the present invention, the block includes the second wall surface angle θ2c at the end portion on the tire rotation direction first arrival side and the second wall surface angle θ2k at the end portion on the rear arrival side in the tire rotation direction. The pneumatic tire according to claim 2, wherein a difference in angle θ2c−θ2k with respect to 2 is 2 to 45 degrees.

  In the invention according to claim 5, in the block, the first wall surface angle θ1c at the end portion on the tire rotation direction first arrival side is the second wall surface angle θ2k at the end portion on the rear arrival side in the tire rotation direction. The pneumatic tire according to any one of claims 2 to 4, which is smaller than the pneumatic tire.

  According to a sixth aspect of the present invention, in the block cross section orthogonal to the third block outer edge, which is an intersection line between the lateral wall surface on the tire rotation direction first arrival side and the tread surface, the block is located on the side in the tire rotation direction first arrival side. A third wall surface angle θ3, which is an angle formed between the wall surface and the normal line of the tread standing on the outer edge of the third block, gradually increases from the tire equator side toward the ground contact end side, and the tire rotation direction rear landing side Between the horizontal wall surface on the rear landing side in the tire rotation direction and the normal line of the tread standing on the outer edge of the fourth block in the block cross section orthogonal to the fourth block outer edge, which is the intersection line of the horizontal wall surface and the tread surface The pneumatic tire according to any one of claims 1 to 5, wherein a fourth wall surface angle θ4, which is an angle, gradually increases from the ground contact end side toward the tire equator side.

  The invention according to claim 7 is the pneumatic tire according to any one of claims 1 to 6, wherein the block has a parallelogram shape on the tread surface.

In the pneumatic tire of the present invention, a block is formed in the tread portion, and the angle of the outer edge of the first block, which is a line of intersection between the vertical wall surface on the tire equator side and the tread surface, is α1U, the tire equator side The angle of the inner edge of the first block, which is the line of intersection between the vertical wall surface of the tire and the vertical groove on the tire equator side, with respect to the tire circumferential direction is α1L, and the second line is the line of intersection between the vertical wall surface on the ground contact end side and the tread surface The angle of the outer edge of the block with respect to the tire circumferential direction is α2U, and the angle of the second block inner edge with respect to the tire circumferential direction, which is a line of intersection between the vertical wall surface on the grounding end side and the groove bottom of the vertical groove on the grounding end side, is α2L. When the following expressions (1) and (2) are satisfied.
5 degrees ≦ α1L <α1U ≦ 30 degrees (1)
10 degrees ≦ α2L <α2U ≦ 35 degrees (2)

  In such a block, since the inner edge of each block approaches the tire circumferential direction, drainage resistance on the groove bottom side is reduced, and drainage performance is improved. Further, the first block wall surface on the tire equator side has a gentle slope toward the rear arrival side in the tire rotation direction, and the second block wall surface on the ground contact end side has a gentle slope toward the first arrival side in the tire rotation direction. It becomes possible to increase the rigidity of the. Accordingly, the rigidity of the block is improved without impairing the drainage performance, and the steering stability performance is improved.

In the pneumatic tire of the present invention, at the above-described angle,
α1L <α2L (3)
α1U <α2U (4)
Satisfy the relationship.

  Thereby, the drainage resistance of the longitudinal groove on the tire equator side, which is originally difficult to drain, is reduced, and the drainage performance is further improved. In addition, on the ground contact end side of the block, the rigidity of the block is improved, and the steering stability performance is further improved.

It is an expanded view of the tread part of the pneumatic tire of one embodiment of the present invention. It is the elements on larger scale of FIG. It is a top view of the 1st block of this embodiment. It is a perspective view of the 1st block. It is the perspective view of the 1st block seen from the direction different from FIG. It is an expanded view of the tread part showing the other Example of this invention. It is an expanded view of the tread part showing the comparative examples 1 thru | or 4.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIGS. 1 and 2, the pneumatic tire (not shown) of the present embodiment has a longitudinal groove 3 extending in the tire circumferential direction on the tread portion 2 and a direction intersecting with the longitudinal groove 3. A lateral groove 4 is formed. Accordingly, the tread portion 2 is formed as a tread pattern in which a plurality of blocks 5 are divided by the grooves 3 and 4.

  The tread pattern is a so-called directional pattern in which the tire rotation direction R is designated. The rotation direction R causes the tread pattern to exhibit the most effective drainage performance. In the tread pattern, the longitudinal grooves 3 and the lateral grooves 4 are arranged substantially line-symmetrically with the tire equator C as the center. However, the present invention is not limited to such a mode.

  In the present embodiment, the longitudinal groove 3 is provided on one outer side in the tire axial direction and is relatively small with respect to the tire circumferential direction, and the first longitudinal groove 3a extending on the tire equator C. A pair of second longitudinal grooves 3b inclined at an angle, and a pair of third longitudinal grooves 3c disposed on both outer sides in the tire axial direction and inclined at an angle larger than the longitudinal grooves 3b. Including.

  The first longitudinal groove 3a extends on the tire equator C. Thereby, the 1st vertical direction groove | channel 3a can drain | emit the water of the crown area | region where a ground contact pressure is high at the time of a straight running. Further, the second vertical groove 3b and the third vertical groove 3c are inclined at an angle β in such a direction that the position of the groove becomes the outer side in the tire axial direction as the rotation of the tire proceeds. This is useful for guiding water on the road surface from the inner side to the outer side in the tire axial direction by utilizing the rotation of the tire.

  In the present embodiment, the lateral groove 4 includes the first lateral groove 4a, the second longitudinal groove 3b, and the second longitudinal groove that connect between the first longitudinal groove 3a and the second longitudinal groove 3b. The second horizontal groove 4b that connects between the three vertical grooves 3c, and the third horizontal groove 4c that connects between the third vertical groove 3c and the ground contact Te.

  The first, second and third lateral grooves 4a, 4b and 4c are inclined at angles γ1, γ2 and γ3 with respect to the tire axial direction, respectively. Each of these lateral grooves 4a to 4c is also inclined so that the position of the groove is away from the tire equator C as the rotation of the tire proceeds. Further, the first to third lateral grooves 4 a to 4 c are arranged so as to be substantially continuous via the longitudinal groove 3. Thereby, the drainage of the first vertical groove 3a can be effectively guided to the grounding end Te side by using the ground pressure of the tire. The angle γ is an angle formed by the center line of the groove width of each lateral groove.

  In the present embodiment, it is desirable that the angles γ1 to γ3 satisfy the relationship γ1> γ2> γ3. As a result, the lateral grooves 4 in the central region of the tread portion 2 are brought closer to the tire circumferential direction, the drainage resistance is reduced, and the drainage performance is further enhanced. Further, the lateral groove on the ground contact end side is brought close to the tire axial direction, and the rigidity of the block is increased to improve the steering stability.

  Although not limited, as a preferred embodiment, the angle γ1 of the first lateral groove 4a is preferably 50 degrees or more, more preferably 60 degrees or more. However, if the angle γ1 is too large, the block rigidity may be excessively lowered. Therefore, it is preferably 80 degrees or less, more preferably 70 degrees or less.

  Similarly, the angle γ3 of the third lateral groove 4c is preferably 40 degrees or less, more preferably 20 degrees or less, and may be 0 degrees (that is, parallel to the tire axial direction).

  Moreover, the groove width W and the groove depth D of the vertical groove 3 and the horizontal groove 4 can be appropriately determined according to the custom. In the case of a tire for passenger cars, for example, the groove width W is preferably 3 mm or more, more preferably 5 mm or more, and preferably 20 mm or less, more preferably 15 mm or less. Similarly, the groove depth D (shown in FIG. 3) is preferably 1.5 mm or more, more preferably 3 mm or more, and preferably 8 mm or less, more preferably 6 mm or less.

  Due to the longitudinal grooves 3 and the lateral grooves 4 as described above, the tread portion 2 includes a first block 5a partitioned between the first longitudinal groove 3a and the second longitudinal groove 3b. The second block row in which the first block row Br1 arranged in the circumferential direction and the second block 5b partitioned between the second longitudinal groove 3b and the third longitudinal groove 3c are arranged in the tire circumferential direction. A third block row Br3 is formed in which Br2, the third block 5c partitioned between the third longitudinal groove 3c and the ground contact Te is arranged in the tire circumferential direction.

  FIG. 3 shows an enlarged view of the first block 5a of FIG. FIG. 4 is a perspective view thereof. 3 and 4, the first block 5a includes a longitudinal groove 3A on the tire equator side, a longitudinal groove 3B on the ground contact end side, and a lateral groove 4A on the tire rotation direction first arrival side. And the lateral groove 4B on the rear arrival side in the tire rotation direction.

Here, the longitudinal groove 3A on the tire equator side and the longitudinal groove 3B on the ground contact end side mean the tire equator side and the ground contact end side as relative positions viewed from the block, respectively. Therefore, for the first block 5a and the second block 5b, these grooves are as follows.
<First block 5a>
The longitudinal groove 3A on the tire equator side ... the first longitudinal groove 3a
Longitudinal groove 3B on the grounding end side ... second longitudinal groove 3b
<Second block 5b>
The longitudinal groove 3A on the tire equator side ... the second longitudinal groove 3b
Longitudinal groove 3B on the grounding end side ... Third longitudinal groove 3c

  Further, as shown in FIG. 3, the first block 5a includes a tread surface 7 that contacts the road surface, a vertical wall surface 8a on the tire equator side facing the longitudinal groove 3A on the tire equator C side, and a grounding end side. The vertical wall surface 8b on the ground contact side facing the longitudinal groove 3B, the lateral wall surface 8c on the tire rotation direction first arrival side facing the lateral groove 4A on the tire rotation direction first arrival side, and the lateral direction on the rear arrival side in the tire rotation direction And a lateral wall surface 8d on the rear arrival side in the tire rotation direction facing the groove 4B. In addition, the said tread surface 7 of this embodiment is formed in the planar view substantially parallelogram shape by the said vertical direction groove | channel 3 and the horizontal direction groove | channel 4. As shown in FIG.

  Further, as shown in FIG. 3, the vertical wall surface 8a on the tire equator side of the first block 5a has a first block outer edge 9a that is a line of intersection with the tread surface 7, and a longitudinal groove 3A on the tire equator side. A first block inner edge 10a that is a line of intersection with the groove bottom 3As. When an arc-shaped chamfered portion is provided between the groove bottom 3As and the tire equator-side joint wall surface 8a, an intersection line between the chamfered portion and the tire equator-side joint wall surface 8a is defined as a first block extension line. 10a.

  Similarly, the vertical wall surface 8b on the ground contact end side of the first block 5a intersects the second block outer edge 9b, which is a cross line with the tread surface 7, and the groove bottom 3Bs of the vertical groove 3B on the ground contact end side. And a second block inner edge 10b.

  Each of these block outer edges 9a, 9b and each block inner edges 10a, 10b is formed in a straight line shape inclined toward the ground contact Te toward the rear arrival side in the tire rotation direction in this embodiment. It is not limited to such an aspect.

Furthermore, the first block 5a of the present embodiment is formed so as to satisfy the following expressions (1) and (2).
5 degrees ≦ α1L <α1U ≦ 30 degrees (1)
10 degrees ≦ α2L <α2U ≦ 35 degrees (2)
Here, the symbols are as follows.
α1U: angle of the first block outer edge 9a with respect to the tire circumferential direction α1L: angle of the first block inner edge 10a with respect to the tire circumferential direction α2U: angle of the second block outer edge 9b with respect to the tire circumferential direction α2L: second block inner edge 10b Angle relative to tire circumferential direction

  In this way, in the first block 5a, the block inner edges 10a, 10b on the groove bottom side of the vertical wall surfaces 8a, 8b on the tire equator side and the ground contact end side are compared with the block outer edges 9a, 9b on the tread side. It extends at an angle closer to the tire circumferential direction. Such a shape of the vertical wall surface increases drainage performance by reducing drainage resistance on the groove bottom side in the longitudinal groove 3A on the tire equator side and the longitudinal groove 3B on the ground contact end side. Moreover, since the effect | action which improves this drainage performance can be ensured irrespective of the tread 7 of the 1st block 5a, the rigidity of the 1st block 5a is not substantially impaired.

  Further, the block outer edge 9 and the block inner edge 10 intersect in plan view. In the present embodiment, by making the height D from the groove bottom of the first block 5a constant, the vertical wall surfaces 8a and 8b are each formed by a twisted curved surface rather than a single plane, and the tire equator The block wall surface 8a on the side is inclined toward the rear arrival side in the tire rotation direction, and the block wall surface 8b on the ground contact end side is inclined toward the arrival side in the tire rotation direction.

  More specifically, as shown in FIG. 4, the first block 5a is formed on the vertical wall surface 8a on the tire equator side and the first block outer edge 9a in a block cross section orthogonal to the first block outer edge 9a. The first wall surface angle θ1 formed by the normal line n of the standing tread surface 7 gradually increases from the first arrival side in the tire rotation direction toward the rear arrival side. Further, the first block 5a has a first cross section formed by a vertical wall surface 8b on the grounding end side and a normal line n of the tread surface 7 standing on the second block outer edge 9b in a block cross section orthogonal to the second block outer edge 9b. The wall surface angle θ2 of 2 gradually increases from the rear arrival side in the tire rotation direction toward the first arrival side.

  Accordingly, the tire equator side of the first block 5a is improved in bending rigidity toward the tire rotation direction rear arrival side, and the ground contact end side of the first block 5a is directed toward the tire rotation direction first arrival side. The bending rigidity of the block is improved. Therefore, the pneumatic tire of this embodiment can improve the rigidity of the block in a well-balanced manner without impairing the drainage performance, and the steering stability performance is improved. In particular, in the case where the tread surface of the first block 5a has a parallelogram shape as in the present embodiment, the rigidity of the corner portions 7fb and 7ra on the obtuse angle side is effectively increased, so that the steering stability and uneven wear resistance are improved. Improves.

  The block outer edge 9 and the block inner edge 10 can adopt various shapes, but are preferably linear from the viewpoint of reducing drainage resistance. However, for example, in order to further secure the groove volume of the longitudinal groove 3 while suppressing a decrease in the land ratio, the block inner edge 10 has a central portion of the block inner edge 10 directed toward the center of the first block 5. A convex arc shape may be used.

In order to exhibit an improvement effect of the drainage performance of the above, the angle α1L respect to the tire circumferential direction of the first radially inner edge 10a is from the viewpoint of increasing the block stiffness shall be the 5 degrees or more.

In addition, the angle α1U of the first block outer edge 9a with respect to the tire circumferential direction is larger than the angle α1L. However, if this angle is excessively large, the tread surface 7 of the first block 5a becomes small and the land ratio becomes small. Decrease. For this reason, there exists a possibility that block rigidity may fall and steering stability may fall. From this standpoint, the angle α1U the Ru defined below 30 degrees with respect to the tire circumferential direction of the first outer edge 9a.

  In the vertical wall surface 8a on the tire equator side of the present embodiment, the block rigidity is improved by the difference between the angle α1U of the first block outer edge 9a and the angle α1L of the first block inner edge 10a as described above. Therefore, when these angle differences α1U−α1L are reduced, the above-described effects tend to be relatively lowered. On the other hand, when the angle difference α1U−α1L is increased, the rigidity of the block is greatly different in the circumferential direction, and there is a possibility that uneven wear occurs in the low rigidity portion. From such a viewpoint, the angle difference α1U−α1L is preferably 5 degrees or more, and preferably 15 degrees or less.

The angle α2L respect to the tire circumferential direction of the second radially inner edge 10b is from the viewpoint of increasing the block stiffness shall be the 10 degrees or more.

In addition, the angle α2U of the second block outer edge 9b with respect to the tire circumferential direction is larger than the angle α2L. However, if the angle is excessively large, the first block 5a tread surface 7 becomes small and the land ratio decreases. To do. For this reason, there exists a possibility that block rigidity may fall and steering stability may fall. From this standpoint, the angle α2U respect to the tire circumferential direction of the second outer edge 9b is Ru defined below 35 degrees.

  Similarly to the vertical wall surface 8a on the tire equator side, when the difference α2U−α2L between the angle α2U of the second block outer edge 9b and the angle α2L of the second block inner edge 10b is reduced, the above-described block rigidity improvement effect is relatively increased. There is a tendency to decrease. On the other hand, when the angle difference α2U−α2L is increased, there is a possibility that uneven wear may occur. From such a viewpoint, the angle difference α2U−α2L is preferably 5 degrees or more, and preferably 15 degrees or less.

Furthermore, the above-described angles satisfy the following expressions (3) and (4).
α1L <α2L (3)
α1U <α2U (4)

  That is, the block outer edge 9a and the block inner edge 10a on the tire equator side extend so as to approach a smaller angle, that is, a tire circumferential line, than the block outer edge 9b and the block inner edge 10b on the ground contact end side, respectively. As a result, the drainage resistance of the longitudinal groove 3A on the tire equator C side where the contact pressure is high is further reduced, and the drainage on the tire equator C side is performed more smoothly. In addition, the above-mentioned angle definition improves the rigidity of the first block 5a on the ground contact end side, and improves steering stability.

  In addition, in order to make drainage performance and steering stability compatible at a higher level, as a result of various experiments, it is desirable that the angle differences α2L−α1L and α2U−α1U are preferably 5 degrees or more. It has been found that preferably 20 degrees or less is desirable. This will become clear in later examples.

  Further, the first wall surface angle θ1 and the second wall surface angle θ2 are not particularly limited, but if the angles θ1 and θ2 are too large, the steering stability may be deteriorated due to a decrease in the land ratio. Conversely, if the angles θ1 and θ2 are too small, it may be difficult to increase the block rigidity. From such a viewpoint, the first wall angle θ1 is preferably 10 degrees or more, and preferably 45 degrees or less. The second wall angle θ2 is preferably 10 degrees or more, and preferably 45 degrees or less.

  Further, in order to make drainage performance and steering stability compatible at a higher level, in the vertical wall surface 8a on the tire equator side, the first wall surface angle θ1c at the end portion 5CA on the arrival side in the tire rotation direction and the tire rotation The angle difference θ1k−θ1c with the first wall surface angle θ1k at the end portion 5CB on the rear side in the direction is preferably 2 degrees or more, more preferably 5 degrees or more, and preferably 45 degrees or less, more Preferably it is 20 degrees or less.

  From the same viewpoint, in the vertical wall surface 8b on the ground contact end side, the second wall surface angle θ2c at the end portion 5TA on the tire rotation direction first arrival side and the second wall surface at the end portion 5TB on the rear arrival side in the tire rotation direction. The angle difference θ2c−θ2k with respect to the angle θ2k is preferably 2 degrees or more, more preferably 5 degrees or more, and preferably 45 degrees or less, more preferably 20 degrees or less.

  Further, in the first block 5a, the first wall surface angle θ1c at the end portion 5CA on the tire rotation direction first arrival side is greater than the second wall surface angle θ2k at the end portion 5TB on the rear arrival side in the tire rotation direction. It is desirable that it is also small. Thereby, since the vertical groove 3A on the tire equator C side having a high contact pressure can be brought close to the tire circumferential direction, drainage performance, particularly hydroplaning performance can be improved. However, even if the difference between the first wall surface angle θ1c and the second wall surface angle θ2k is too large, the second wall surface angle θ2k is increased, and thus drainage tends to be deteriorated due to an increase in drainage resistance.

  From such a viewpoint, the difference θ2k−θ1c between the second wall surface angle θ2k and the first wall surface angle θ1c is preferably 5 degrees or more, and preferably 30 degrees or less.

  Further, as shown in FIG. 5, the first block 5 a is a block cross section orthogonal to the third block outer edge 9 c that is an intersection line between the lateral wall surface 8 c on the tire rotation direction first arrival side and the tread surface 7. A third wall surface angle θ3, which is an angle formed by the lateral wall surface 8c on the tire rotation direction first arrival side and the normal line n of the tread surface 7 standing on the third block outer edge 9c, is from the tire equator C side to the ground contact Te side. It gradually increases toward.

  The first block 5a is a block cross section orthogonal to the fourth block outer edge 9d, which is a line of intersection between the lateral wall surface 8d on the tire rotation direction rear landing side and the tread surface 7, and on the tire rotation direction rear landing side. A fourth wall surface angle θ4, which is an angle formed between the horizontal wall surface 8d and the normal line n of the tread surface 7 standing on the fourth block outer edge 9d, gradually increases from the ground contact end Te side toward the tire equator C side.

  By these, coupled with the shape of the vertical wall surface 8a on the tire equator C side and the vertical wall surface 8b on the ground contact end side, the drainage performance can be further maintained and the block rigidity can be improved.

  Further, in the present embodiment, the third block inner edge 10c and the fourth block inner edge 10d are circles that protrude toward the center of the first block 5 at the center of each of the block inner edges 10c, 10d. It is formed with an arcuate curve. Thereby, the groove | channel volume of the horizontal direction groove | channel 4 can be increased partially, and drainage performance can be improved, suppressing the reduction | decrease in a land ratio.

  The second block 5b also includes vertical wall surfaces 8a and 8b and horizontal wall surfaces 8c and 8d similar to the first block 5a.

  As mentioned above, although embodiment of this invention was explained in full detail, it cannot be overemphasized that this invention is not limited to illustrated embodiment, and can be deform | transformed and implemented in a various aspect.

Test tires based on the tread pattern in FIG. 1 and the specifications in Table 1 were prototyped, and their drainage performance and wear resistance performance were tested. In Comparative Example 1, as shown in FIG. 7 , the inner edge of the block and the outer edge of the block are inclined at the same angle with respect to the tire circumferential direction (parallel to each other) on each vertical wall surface and horizontal wall surface. In Comparative Example 2 and later, any one of the formulas (1) to (4) is not satisfied. The common specifications for tires are as follows.

Tire size: 205 / 55R16
Groove width W: 4-8mm
Groove depth D: 7.5 to 8.5 mm
Land ratio: 65% (Comparative Example 1)
Angle γ1: 50 degrees between the first lateral groove and the tire axial direction Angle γ2: 35 degrees between the second lateral groove and the tire axial direction Angle γ3: 20 between the third lateral groove and the tire axial direction The test method is as follows.

<Drainage performance>
Each test tire was mounted on four wheels of a 3500cc domestic 4WD passenger car with a 7J rim and an internal pressure of 230KPa. Then, on the asphalt road surface with a radius of 100 m, on the course with a water depth of 10 mm and a length of 20 m, the vehicle was entered while increasing the speed stepwise, and the lateral acceleration (lateral G) was measured, and 50-80 km The average lateral G of the front wheels at a speed of / h was calculated. A result is displayed by the index | exponent which sets the comparative example 1 to 100, and so that a numerical value is large, drainage property is high and it is favorable.

<Uneven wear resistance>
The test vehicle traveled on a dry asphalt road surface for 3000 km, the difference in wear amount between one end side and the other end side of the three blocks on the tire circumference was measured, and the average value was obtained. The results are displayed as an index with Comparative Example 1 as 100. The larger the value, the higher the block rigidity and the smaller the wear amount.
Table 1 shows the test results.

  As a result of the test, it was confirmed that the example was improved in block rigidity while maintaining drainage performance as compared with the comparative example.

2 Tread portion 3A Longitudinal groove 3B on the tire equator side Longitudinal groove 4A on the ground contact end side Horizontal groove 4B on the tire rotation direction first arrival side Lateral groove 5 on the tire rotation direction rear arrival side 5 Block 7 Tread surface 8a Vertical on the tire equator side Wall surface 8b Vertical wall surface 8c on the ground contact end side Horizontal wall surface 8d on the tire rotation direction first arrival side Horizontal wall surface 9a on the rear arrival side in the tire rotation direction First block outer edge 9b Second block outer edge 10a First block inner edge 10b Second block Inner edge

Claims (7)

A pneumatic tire with a specified direction of rotation,
In the tread portion, there are blocks divided by a longitudinal groove on the tire equator side, a longitudinal groove on the ground contact end side, a lateral groove on the tire rotation direction first arrival side, and a lateral groove on the tire rotation direction rear arrival side. Prepared,
The block includes a tread surface that contacts the road surface, a vertical wall surface on the tire equator side, a vertical wall surface on the ground end side, a horizontal wall surface on the first arrival side in the tire rotation direction, and a horizontal wall surface on the rear arrival side in the tire rotation direction. With
Α1U is an angle with respect to the tire circumferential direction of the outer edge of the first block, which is an intersection line between the vertical wall surface on the tire equator side and the tread surface,
The angle of the inner edge of the first block, which is the intersection of the vertical wall surface on the tire equator side and the groove bottom of the longitudinal groove on the tire equator side, with respect to the tire circumferential direction is α1L,
And the angle of the second block outer edge, which is a line of intersection between the vertical wall surface on the ground contact end side and the tread surface, with respect to the tire circumferential direction, and the groove between the vertical wall surface on the ground contact end side and the vertical groove on the ground contact end side A pneumatic tire characterized by satisfying the following formulas (1) to (4) when an angle with respect to the tire circumferential direction of the second block inner edge that is a line of intersection with the bottom is α2L.
5 degrees ≦ α1L <α1U ≦ 30 degrees (1)
10 degrees ≦ α2L <α2U ≦ 35 degrees (2)
α1L <α2L (3)
α1U <α2U (4)
In the block cross section orthogonal to the first block outer edge, the block has a first wall angle θ1 formed by a vertical wall surface on the tire equator side and a normal line of a tread surface standing on the first block outer edge. While gradually increasing from the rotation direction first arrival side toward the rear arrival side,
In the block cross section perpendicular to the outer edge of the second block, the block has a second wall surface angle θ2 formed by a vertical wall surface on the grounding end side and a normal line of a tread surface standing on the outer edge of the second block. The pneumatic tire according to claim 1, which gradually increases from the rear arrival side toward the first arrival direction in the tire rotation direction.   The block has an angle difference θ1k−θ1c between the first wall surface angle θ1c at the end portion on the first arrival side in the tire rotation direction and the first wall surface angle θ1k at the end portion on the rear arrival side in the tire rotation direction. The pneumatic tire according to claim 2 which is 2-45 degrees.   The block has an angle difference θ2c−θ2k between the second wall surface angle θ2c at the end portion on the first arrival side in the tire rotation direction and the second wall surface angle θ2k at the end portion on the rear arrival side in the tire rotation direction. The pneumatic tire according to claim 2 which is 2-45 degrees.   5. The block according to claim 2, wherein the first wall surface angle θ <b> 1 c at the end portion on the first arrival side in the tire rotation direction is smaller than the second wall surface angle θ <b> 2 k at the end portion on the rear arrival side in the tire rotation direction. The pneumatic tire according to any one of the above. The block has a block cross section orthogonal to a third block outer edge that is an intersection line of the lateral wall surface on the tire rotation direction first arrival side and the tread surface, and is arranged on the horizontal wall surface on the tire rotation direction first arrival side and the third block outer edge. A third wall surface angle θ3, which is an angle formed with the normal of the standing tread surface, gradually increases from the tire equator side toward the ground contact end side,
In the block cross section orthogonal to the fourth block outer edge, which is a line of intersection between the lateral wall surface on the rear arrival side of the tire rotation direction and the tread surface, the horizontal wall surface on the rear arrival side in the tire rotation direction and the fourth block outer edge are set up. The pneumatic tire according to any one of claims 1 to 5, wherein a fourth wall surface angle θ4, which is an angle formed with a normal line of the tread surface, gradually increases from the ground contact end side toward the tire equator side.   The pneumatic tire according to claim 1, wherein the tread surface of the block has a parallelogram shape.

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